My dad recently recorded a 3h long meeting with a smartphone app (I don't know the name, but I can ask him) and this app records in .m4a files.
The only significant sound in the ambiance were human voices.
I don't know why, but this recording came out with a strong clicking sound that makes it almost impossible to comprehend anything.
The clicking happens together with the audio, the louder the voice, the louder the clicks.
I investigated the waveform and found what seems to be some weird amplitude modulation happening:
This is what the signal looks like up close, this stretch has around 0.15 s of duration.
And those apparently silent parts actually have signal, just very low, but I can amplify.
Do you have any idea of what might have caused that and how I could make it a bit better?
So far the only thing I could think about is to find the pattern of this modulation and apply an inverse modulation, but I'm having trouble figuring out just what this pattern is, IF it has a constant pattern.
If the modulation pattern varies along the signal this is going to be way more complicated.